I'm not sure about this at all, but it does seem to me from other forums that A LOT of people in the USA are diagnosed with DID, but I've never come across someone in Australia who has (although the condition does exist). To me it's a very very rare condition yet so many people in the US seem to have it!
If you use the search engine on this forum there is information about DID & PTSD. Infact I think it's in one of the information sections.
To me DID, is having distinct separate identities & being unaware of the others existence. They are quite separate with different personalities, clothing, likes, dislikes, even different speaking voices. But I am no expert!
My understanding is that dissassociation is a big component of PTSD, I know I suffer. I also know that I feel like there is different 'me's' but in no way do I believe I have DID.
Sometimes in therapy when talking about trauma my therapist has pointed out that I use words like "we didn't like that" (instead of I didn't like that) or when I wrote out one of my traumas, I wrote 'she is fighting him off, and I am feeling scared', and there was quite a few written examples of using the word 'she' instead of 'me' or 'we' instead of 'I'.
My T has also described me as being 'split' and she has described 'splitting off' as an effect of trauma but this is not the same as DID.
Personally if I ever got a diagnosis of DID or schizophrenia or cancer or something else significant I'd get a second opinion. And research, research, research...!